The proposal was made in a report from Secretary-General Ban Ki-moon and coincided with a buildup of tensions in an oil-producing border region where both sides have troops.
The current 10,000-member peacekeeping force in Sudan, known as UNMIS, is expected to remain in place in the north but will gradually reduce its presence in Khartoum.
Ban’s report calls for that force to be kept on for three months after July 9, when the south officially splits from the north, to allow time for a reorganization.
That would enable both sides to work out unresolved issues, “including finding a mutually acceptable arrangement for monitoring the border,” the report said.
Diplomats and U.N. officials told Reuters on condition of anonymity that Khartoum does not want UNMIS to leave Sudan altogether though the Sudanese government would prefer that it be less visible in Khartoum.
Ban’s report said the new force should be called the United Nations Mission in South Sudan, or UNMISS.
South Sudan voted to become independent in a referendum in January but tensions have risen in the oil-producing Abyei border region where both sides have built up forces.
Abyei residents were also supposed to have a referendum in January over whether to join the north or south. Disputes over who could vote derailed that ballot and talks over whether Abyei should be in the north or join the south have stalled.
Ban’s report said Abyei was “the greatest challenge to the implementation of the peace agreement.
A U.N. spokeswoman said on Wednesday that tens of thousands of people fled Abyei region as northern militias accused of helping seize the area over the weekend moved farther south.
Ban told a high-level African Union meeting in Addis Ababa that the north and south should “cease their military operations, withdraw all forces and armed elements from the Abyei area, and desist from further acts of aggression, including attacks on U.N. peacekeepers.”
The proposed new force will have to be approved by the U.N. Security Council, which visited Khartoum this week but was snubbed by senior northern officials. The council will hold closed-door consultations on Sudan on May 27.